[PATCH v6 10/10] RAS: add firmware-first CPER provider

[Ahmed Tiba]

Add a firmware-first CPER provider that reuses the shared
GHES helpers, wire it into the RAS Kconfig/Makefile and
document it in the admin guide.

Update MAINTAINERS now that the driver exists.

Signed-off-by: Ahmed Tiba <ahmed.tiba@xxxxxxx>
---
 Documentation/admin-guide/RAS/main.rst |  15 ++
 MAINTAINERS                            |   1 +
 drivers/acpi/apei/apei-internal.h      |   3 +-
 drivers/ras/Kconfig                    |  11 ++
 drivers/ras/Makefile                   |   1 +
 drivers/ras/cper-esource.c             | 322 +++++++++++++++++++++++++++++++++
 6 files changed, 351 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/RAS/main.rst b/Documentation/admin-guide/RAS/main.rst
index 5a45db32c49b..d4e3c8c1b92f 100644
--- a/Documentation/admin-guide/RAS/main.rst
+++ b/Documentation/admin-guide/RAS/main.rst
@@ -205,6 +205,21 @@ Architecture (MCA)\ [#f3]_.
 .. [#f3] For more details about the Machine Check Architecture (MCA),
   please read Documentation/arch/x86/x86_64/machinecheck.rst at the Kernel tree.
 
+Firmware-first CPER providers
+-----------------------------
+
+Some systems expose Common Platform Error Record (CPER) data through
+platform firmware, with the error source described in DeviceTree.
+Enable ``CONFIG_RAS_CPER_ESOURCE`` to support those providers. The
+current in-tree binding is
+``Documentation/devicetree/bindings/firmware/arm,ras-cper.yaml``.
+
+The DeviceTree node describes the firmware-owned status buffer and ack
+buffer used to exchange CPER data with the OS. The driver reuses the
+shared GHES CPER handling helpers, so parsing, logging, notifier
+delivery, and memory failure handling follow the same paths as ACPI
+GHES whether the error source is described by ACPI or DeviceTree.
+
 EDAC - Error Detection And Correction
 *************************************
 
diff --git a/MAINTAINERS b/MAINTAINERS
index 5aa495fdff72..00b9a1abab67 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -22326,6 +22326,7 @@ RAS ERROR STATUS
 M:	Ahmed Tiba <ahmed.tiba@xxxxxxx>
 S:	Maintained
 F:	Documentation/devicetree/bindings/firmware/arm,ras-cper.yaml
+F:	drivers/ras/cper-esource.c
 
 RAS INFRASTRUCTURE
 M:	Tony Luck <tony.luck@xxxxxxxxx>
diff --git a/drivers/acpi/apei/apei-internal.h b/drivers/acpi/apei/apei-internal.h
index 77c10a7a7a9f..15d11f10d067 100644
--- a/drivers/acpi/apei/apei-internal.h
+++ b/drivers/acpi/apei/apei-internal.h
@@ -123,8 +123,7 @@ struct dentry *apei_get_debugfs_dir(void);
 static inline u32 cper_estatus_len(struct acpi_hest_generic_status *estatus)
 {
 	if (estatus->raw_data_length)
-		return estatus->raw_data_offset + \
-			estatus->raw_data_length;
+		return estatus->raw_data_offset + estatus->raw_data_length;
 	else
 		return sizeof(*estatus) + estatus->data_length;
 }
diff --git a/drivers/ras/Kconfig b/drivers/ras/Kconfig
index fc4f4bb94a4c..3c1c63b2fefc 100644
--- a/drivers/ras/Kconfig
+++ b/drivers/ras/Kconfig
@@ -34,6 +34,17 @@ if RAS
 source "arch/x86/ras/Kconfig"
 source "drivers/ras/amd/atl/Kconfig"
 
+config RAS_CPER_ESOURCE
+	bool "Firmware-first CPER error source block provider"
+	select GHES_CPER_HELPERS
+	help
+	  Enable support for firmware-first Common Platform Error Record
+	  (CPER) error source block providers. The current in-tree user is
+	  described by the arm,ras-cper DeviceTree binding. The driver
+	  reuses the existing GHES CPER helpers so the error processing
+	  matches the ACPI code paths, but it can be built even when ACPI is
+	  disabled.
+
 config RAS_FMPM
 	tristate "FRU Memory Poison Manager"
 	default m
diff --git a/drivers/ras/Makefile b/drivers/ras/Makefile
index 11f95d59d397..0de069557f31 100644
--- a/drivers/ras/Makefile
+++ b/drivers/ras/Makefile
@@ -2,6 +2,7 @@
 obj-$(CONFIG_RAS)	+= ras.o
 obj-$(CONFIG_DEBUG_FS)	+= debugfs.o
 obj-$(CONFIG_RAS_CEC)	+= cec.o
+obj-$(CONFIG_RAS_CPER_ESOURCE)	+= cper-esource.o
 
 obj-$(CONFIG_RAS_FMPM)	+= amd/fmpm.o
 obj-y			+= amd/atl/
diff --git a/drivers/ras/cper-esource.c b/drivers/ras/cper-esource.c
new file mode 100644
index 000000000000..cc9f5f522400
--- /dev/null
+++ b/drivers/ras/cper-esource.c
@@ -0,0 +1,322 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Firmware-first CPER error source provider.
+ *
+ * This driver shares the GHES CPER helpers so we keep the reporting and
+ * notifier behaviour identical to ACPI GHES.
+ *
+ * Copyright (C) 2026 ARM Ltd.
+ * Author: Ahmed Tiba <ahmed.tiba@xxxxxxx>
+ */
+
+#include <linux/bitops.h>
+#include <linux/cleanup.h>
+#include <linux/cper.h>
+#include <linux/idr.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/panic.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include <acpi/ghes.h>
+#include <acpi/ghes_cper.h>
+
+static DEFINE_IDA(cper_esource_source_ids);
+
+struct cper_esource_ack {
+	void *addr;
+	u64 preserve;
+	u64 set;
+	u8 width;
+	bool present;
+};
+
+struct cper_esource {
+	struct device *dev;
+	void *status;
+	size_t status_len;
+
+	struct cper_esource_ack ack;
+
+	struct acpi_hest_generic generic;
+	struct acpi_hest_generic_status *estatus;
+
+	int irq;
+
+	/* Serializes access while firmware and the OS share the status buffer. */
+	spinlock_t lock;
+};
+
+static void *cper_esource_map_region(struct device *dev, unsigned int index,
+				     size_t *size)
+{
+	struct resource res;
+	void *addr;
+
+	if (of_reserved_mem_region_to_resource(dev->of_node, index, &res))
+		return ERR_PTR(dev_err_probe(dev, -EINVAL,
+					     "unable to resolve memory-region %u\n",
+					     index));
+
+	*size = resource_size(&res);
+	if (!*size)
+		return ERR_PTR(dev_err_probe(dev, -EINVAL,
+					     "memory-region %u has zero length\n",
+					     index));
+
+	addr = devm_memremap(dev, res.start, *size, MEMREMAP_WB);
+	if (!addr)
+		return ERR_PTR(dev_err_probe(dev, -ENOMEM,
+					     "failed to map memory-region %u\n",
+					     index));
+
+	return addr;
+}
+
+static void cper_esource_release_source_id(void *data)
+{
+	struct cper_esource *ctx = data;
+
+	ida_free(&cper_esource_source_ids, ctx->generic.header.source_id);
+}
+
+static int cper_esource_init_pool(void)
+{
+	return ghes_estatus_pool_init(1);
+}
+
+static u32 cper_esource_estatus_len(struct acpi_hest_generic_status *estatus)
+{
+	if (estatus->raw_data_length)
+		return estatus->raw_data_offset + estatus->raw_data_length;
+	else
+		return sizeof(*estatus) + estatus->data_length;
+}
+
+static int cper_esource_validate_status(struct cper_esource *ctx)
+{
+	size_t estatus_len;
+
+	if (!ctx->estatus->block_status)
+		return -ENOENT;
+
+	if (cper_estatus_check_header(ctx->estatus))
+		return -EINVAL;
+
+	if (ctx->estatus->raw_data_length &&
+	    (ctx->estatus->raw_data_offset > ctx->status_len ||
+	     ctx->estatus->raw_data_length >
+	     ctx->status_len - ctx->estatus->raw_data_offset))
+		return -EINVAL;
+
+	estatus_len = cper_esource_estatus_len(ctx->estatus);
+	if (estatus_len < sizeof(*ctx->estatus) || estatus_len > ctx->status_len)
+		return -EINVAL;
+
+	if (cper_estatus_check(ctx->estatus))
+		return -EINVAL;
+
+	return 0;
+}
+
+static void cper_esource_ack(struct cper_esource *ctx)
+{
+	if (!ctx->ack.present)
+		return;
+
+	if (ctx->ack.width == 64) {
+		u64 *addr = ctx->ack.addr;
+		u64 val = READ_ONCE(*addr);
+
+		/* Publish status-buffer updates before raising the ack bit. */
+		wmb();
+		val &= ctx->ack.preserve;
+		val |= ctx->ack.set;
+		WRITE_ONCE(*addr, val);
+	} else {
+		u32 *addr = ctx->ack.addr;
+		u32 val = READ_ONCE(*addr);
+
+		/* Publish status-buffer updates before raising the ack bit. */
+		wmb();
+		val &= (u32)ctx->ack.preserve;
+		val |= (u32)ctx->ack.set;
+		WRITE_ONCE(*addr, val);
+	}
+}
+
+static void cper_esource_clear_status(struct cper_esource *ctx)
+{
+	ctx->estatus->block_status = 0;
+	WRITE_ONCE(((struct acpi_hest_generic_status *)ctx->status)->block_status, 0);
+}
+
+static void cper_esource_fatal(struct cper_esource *ctx)
+{
+	__ghes_print_estatus(KERN_EMERG, &ctx->generic, ctx->estatus);
+	add_taint(TAINT_MACHINE_CHECK, LOCKDEP_STILL_OK);
+	panic("GHES: fatal firmware-first CPER record from %s\n",
+	      dev_name(ctx->dev));
+}
+
+static void cper_esource_process(struct cper_esource *ctx)
+{
+	int rc;
+	int sev;
+
+	guard(spinlock_irqsave)(&ctx->lock);
+
+	memcpy(ctx->estatus, ctx->status, ctx->status_len);
+
+	rc = cper_esource_validate_status(ctx);
+	if (rc == -ENOENT)
+		return;
+	if (rc) {
+		dev_warn_ratelimited(ctx->dev, FW_WARN GHES_PFX
+				     "Invalid error status block\n");
+		cper_esource_clear_status(ctx);
+		cper_esource_ack(ctx);
+		return;
+	}
+
+	sev = ghes_severity(ctx->estatus->error_severity);
+	if (sev >= GHES_SEV_PANIC)
+		cper_esource_fatal(ctx);
+
+	ghes_print_estatus(NULL, &ctx->generic, ctx->estatus);
+
+	ghes_cper_handle_status(ctx->dev, &ctx->generic, ctx->estatus, false);
+	cper_esource_clear_status(ctx);
+	cper_esource_ack(ctx);
+}
+
+static irqreturn_t cper_esource_irq(int irq, void *data)
+{
+	struct cper_esource *ctx = data;
+
+	cper_esource_process(ctx);
+
+	return IRQ_HANDLED;
+}
+
+static int cper_esource_init_ack(struct cper_esource *ctx)
+{
+	struct device *dev = ctx->dev;
+	size_t size;
+
+	ctx->ack.addr = cper_esource_map_region(dev, 1, &size);
+	if (IS_ERR(ctx->ack.addr))
+		return PTR_ERR(ctx->ack.addr);
+
+	switch (size) {
+	case 4:
+		ctx->ack.width = 32;
+		ctx->ack.preserve = ~0U;
+		break;
+	case 8:
+		ctx->ack.width = 64;
+		ctx->ack.preserve = ~0ULL;
+		break;
+	default:
+		return dev_err_probe(dev, -EINVAL,
+				     "unsupported ack resource size %zu\n", size);
+	}
+
+	ctx->ack.set = BIT_ULL(0);
+	ctx->ack.present = true;
+	return 0;
+}
+
+static int cper_esource_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct cper_esource *ctx;
+	size_t size;
+	int source_id;
+	int rc;
+
+	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	spin_lock_init(&ctx->lock);
+	ctx->dev = dev;
+
+	ctx->status = cper_esource_map_region(dev, 0, &size);
+	if (IS_ERR(ctx->status))
+		return PTR_ERR(ctx->status);
+
+	ctx->status_len = size;
+	if (ctx->status_len < sizeof(*ctx->estatus))
+		return dev_err_probe(dev, -EINVAL,
+				     "status region is smaller than a CPER header\n");
+
+	rc = cper_esource_init_ack(ctx);
+	if (rc)
+		return rc;
+
+	rc = cper_esource_init_pool();
+	if (rc)
+		return rc;
+
+	ctx->estatus = devm_kzalloc(dev, ctx->status_len, GFP_KERNEL);
+	if (!ctx->estatus)
+		return -ENOMEM;
+
+	/* Keep source_id 0 unused so a zeroed header is never treated as valid. */
+	source_id = ida_alloc_min(&cper_esource_source_ids, 1, GFP_KERNEL);
+	if (source_id < 0)
+		return source_id;
+	if (source_id > U16_MAX) {
+		ida_free(&cper_esource_source_ids, source_id);
+		return -ENOSPC;
+	}
+
+	ctx->generic.header.type = ACPI_HEST_TYPE_GENERIC_ERROR;
+	ctx->generic.header.source_id = source_id;
+
+	rc = devm_add_action_or_reset(dev, cper_esource_release_source_id,
+				      ctx);
+	if (rc)
+		return rc;
+
+	ctx->generic.notify.type = ACPI_HEST_NOTIFY_EXTERNAL;
+	ctx->generic.error_block_length = ctx->status_len;
+
+	ctx->irq = platform_get_irq(pdev, 0);
+	if (ctx->irq < 0)
+		return ctx->irq;
+
+	rc = devm_request_threaded_irq(dev, ctx->irq, NULL, cper_esource_irq,
+				       IRQF_ONESHOT,
+				       dev_name(dev), ctx);
+	if (rc)
+		return dev_err_probe(dev, rc, "failed to request interrupt\n");
+
+	return 0;
+}
+
+static const struct of_device_id cper_esource_of_match[] = {
+	{ .compatible = "arm,ras-cper" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, cper_esource_of_match);
+
+static struct platform_driver cper_esource_driver = {
+	.driver = {
+		.name = "cper-esource",
+		.of_match_table = cper_esource_of_match,
+	},
+	.probe = cper_esource_probe,
+};
+
+module_platform_driver(cper_esource_driver);
+
+MODULE_AUTHOR("Ahmed Tiba <ahmed.tiba@xxxxxxx>");
+MODULE_DESCRIPTION("Firmware-first CPER provider");
+MODULE_LICENSE("GPL");

-- 
2.43.0